Air brake slack adjuster



May 28, 1946. A. McEwEN 'AIRBRAKE sLAcK ADJUSTER Filed April 11, 1944 Q L SMQ/wm 5 McEwen atened May Z,

crie 1 Claim.

This invention relates to air brake systems, and more particularly to mechanism for automatically adjusting the throw of the operating levers to l vide simple, positive means to automatically adjust the brake linkage as the brake is applied to l maintain a constant piston 'stroke regardless of the amount of Wear of the brake shoes.

.A further object ofthe invention is to provide such adjusting means positioned at a point in the brake operating mechanism Where equal adjustment will be eiected on the brakes of both o trucks, thus maintaining an edualized braking system and reducing the danger of line defects such as slid flats and brake burns.

Another object of the invention is to provide means to automatically release the brake operatling linkage from the hollow-piston at the end of each retraction stroke of the piston, and to automatically'connect the piston and linkage at the beginning of the operating stroke. This ensures the brake'linkage being returned to brake-releasing position and permits hand operation of the brakes when desired without the heavy drag caused by moving the piston.

Other objects will become apparent from the following description taken in conjunction with the drawing which accompany and form ,a part of this speciiication and throughout the several figures of which the,` same characters of reference are used to denote identical parts.

In the drawing: v

Figure 1 is a perspective view of a portion of a conventional brake system including brake piston. levers and linkage with the device ofthepresent invention attached thereto;

Figure 2 is a 4sectional View showing *he adjusting screw and related structure;

Figure 3 is a sectional view taken'on the line 3-3 of Figure 2; and,

' Figure 4 is a longitudinal sectional view taken (ci. isc-2cm) maintain standard brake-piston movement,with

thru the brake cylinder, piston and piston rod with the piston-releasing mechanism in place.

Referring to the drawing in detail, I represents a conventional brake cylinder having a piston rod 2 extending therefrom. The piston rod 2 is pivotally connected, as at 3, to one endof an operating lever l which is pivotally connected at 5-to a brake operating rod E. A companion operating lever l is pivotally mounted as at 8 at the opposite side of the cylinder I, and connects to a brake operating lever 9. A tierd I0 couples the levers `4 andl for simultaneous opration.

This is. the usual brake system, the movement of To prevent the piston II from increasing its stroke as the brakes wear, means are provided to shorten the tierod I0 simultaneously with, `and in direct proportion to, the wear of the brake shoes. To accomplish this the tierod is composed of two sections I2 and I3. Part I2 is provided `with 4a U-shaped fitting I 4 having one of its upstanding arms I5 secured to the end of the section I2, and its other upstanding arm I6 bored and tapped to receive one end of a screw threaded connector I l, The section I3 is in the form of a bracket pivotally attached to the lever 4 and having an arm I8 threaded to receive the opposite end of the threaded connector I1. ,The connector I1 is threaded oppositely from its middle outwardly. This construction provides av turnbuckle arrangement whereby rotation of the connector will Vary the length of the tiered.

The connector I'I carries a ratchet I9 xedly l positioned midway between its ends. A Weighted for cooperation with the ratchet.

lever 211 straddles the ratchet and is journaled for free rotation upon the connector. The lever comprises the central arm 2I and the spaced armsl slot 25 thru which a cam rod 26 passes. The cam rod is loosely connected to the operating lever 4 at a point closely adjacent the connection between th'e lever l and the piston rod 2, whereby the movement ofthe cam rod will closely approximate that of the brake piston. A guidel 2l for the cam rod is rigidly connected to a sill or -other -xed portion of the .car frame, and supports the outer end of the cam rod. The cam rod is bent to form two guide-contacting surfaces 28 and 29, joined by an incline 3B.

In operation, the brake piston moves outward- 1y rocking the lever 4 which' draws the cam rod with it, sliding it-across the guide 2. If the brake shoesare properly adjusted, the brakes will be fully applied before the brake piston has moved far enoughy to bring the inclined portion 30 of the cam rod into contact with the guide 21. As the brakes wear, the Apiston stroke becomes longer and the-movement of the cam rod greater.- As the stroke approaches the predetermined limit of eiiiciency the inclined surface 30 contacts the guide 2 and lifts the cam' rod. LThis vrocks the Y .weighted lever upward, shifting the pawl 24 into engagement with another tooth on the ratchet I9.

The return stroke of the piston moves the cam rod back to its original position, permitting the weighted leverto drop, rotating the threaded connector Il and shortening the eective length of the tierod Il). Thusthe necessity for a steadily increasing piston stroke is prevented.

It is frequently desirable to operate the brake system by hand. To make the hand operation practical, th'e system should be relieved of the heavy drag of the hollow piston which would be operating against a vacuum during hand opera-fV brake cylinder housesa hollow piston Il which is normally urged to brake-release position by means of spring 3I. The Piston rod, whichv has been referred to in its entirety by the numeral 2, is composed of two parts, the piston rod proper 32 which is hollow and the piston push rod 33 which telescopes Within the hollow piston rod.

As the hollow piston moves outwardly the push rod seats against th'e bottom of the recess in the piston rod and is forced outwardly with the piston, thus moving the brake levers to apply the brakes. When the brakes are to be released, vthe piston moves backward under the influence of the spring 3l.

To ensure the levers returning to their inop- 5 erativeposition, the end of the piston rod is provided with an annular collar 34 and th push rod carries a hook 35 fixed upon a horizontal pivot and free to swing in a vertical plane'. The hook is so positioned that it will engage the collar 84 so that when the piston returns to inoperative position the push' -rod and its attached brake linkage will be drawn back with it.

To automatically release the hollow piston from the lever system to provide for hand operation, a bracket 36 is attached to the cylinder'head. The hook has its forward end formed as a cam to ride up on the bracket 36 as the piston nears its inner limit to release the hook from the collar. The hook remains disengaged, permitting hand operation of the brakes until such time as the piston again moves outwardly, whereupon the latch slides oil of the bracket and reengages the collar on the piston rod.

Although a preferred and practical embodiment of th'e invention has-been shown and de scribed herein, it is to be understood that changes from the exact structure disclosed may be made without departing from the spirit 'of the invention as defined in the appended claim.

What I claim is: y Slack adjuster for railway car brake system having a brake piston, an operating lever connectedto said piston, a second operating lever, and a tierod connecting the levers; a threaded take-up included as `a portion of said tierod, a cam rod loosely connectedto said rst mentioned lever closely adjacent to said brake piston, a, ilxed guide for said cam rod to lift said cam rod when 'said cam rod` is moved beyond a predetermined distance relative to said ilxed guide during the application of the brake system, a weighted lever pivoted on said take-up and having a.y slot through which said cam rod passes,- said weighted lever being positioned between said, xed guide and said first mentioned lever, a ratchet on said takeup, and a pawl carried by said weighted lever for cooperation with said'ratchet, whereby said weighted lever will be raisedand said pawl advanced on said ratchetwhen said cam rod is lifted, and said weighted lever will serve to rotate said take-up during subsequent brake release movement.

ALVA MCEWEN. 

